The specific aims of the proposed research are to analyze genetic differentiation between 6 species in the Aedes albopictus subgroup and to genetically characterize geographic variation in the widespread species, A. albopictus. The Aedes (Stegomyia) albopictus subgroup consists of 11 species of which A. albopictus is the most important. It is a vector of dengue fever and dengue hemorrhagic fever in southeast Asia. Its wide distribution extends from Madagascar to Hawaii. In recent years it has extended its range to Guam, the south Pacific and has even been reported in light traps in Memphis, TN. Surprisingly, little work has been done on the genetics of this or other related species in the subgroup. The proposed research will help bridge this gap. The long term objectives are to utilize the genetic characterization of A. albopictus populations as well as certain related species in the subgroup to evaluate their potential to serve as efficient vectors of dengue fever. The proposed genetic studies will provide the necessary foundation for future analyses on genetics of dengue transmission and competence of species and strains to transmit the disease. The specific aims, to characterize genetic variation within A. albopictus and between species in the albopictus subgroup, will be accomplished through four different types of analyses. Indirect measures of genetic divergence will be obtained through: 1) experimental hybridization with data collected on insemination, embryonation and egg hatch rates and on the viability of hybrid and backcross progeny, and 2) mate choice tests using species pairs in a series of replicates designed to produce indices of sexual isolation. Direct measures of genetic divergence will be obtained from analyses of chromosome differentiation and electrophoretic detection of enzyme variability. Chromosome differentiation will be examined through a series of studies including Giemsa C-banding to localize heterochromatin, meiotic analysis of hybrids and electrophoretically derived linkage map comparisons to determine the presence of inversions, translocations and deletions or duplications, and cytophotometric analysis of nuclear DNA content. UPGMA clustering and principal component analysis of allele frequency data obtained from allozyme studies will be used to differentiate populations into subsets. If certain diagnostic alleles, loci or discrete allelic frequency differences or chromosomal variants exist among geographic strains of A. albopictus from dengue epidemic versus non-epidemic areas, vector competence may become effectively marked.